Most automobiles or other devices powered by an internal combustion engine, such as watercraft, etc., rely at least in part on a battery as part of its power source. For example, an automobile needs a battery to start the engine operating (the engine must be spun up to speed externally before they can operate). Once the engine is operating or running, the battery is charged by a generator connected to the engine. The battery is usually able to store enough charge for the periods that the engine is not running in order to start the engine when needed.
There are many things that will cause a battery to lose its charge, such as leaving the lights on or playing the radio after the engine is turned off, or a short circuit in the battery which drains the battery. When there is not enough charge in the battery, the engine cannot be started, i.e. the battery is discharged. As a result, the battery must be recharged or boosted by another power source. Very often another vehicle is brought to the vicinity of the vehicle with the discharged battery to jump start the vehicle. Another solution was proposed by U.S. Pat. No. 5,589,292 which provides a portable booster battery to recharge the discharged battery.
One concern in using a portable battery such as the portable booster battery disclosed U.S. Pat. No. 5,589,292 to charge batteries that have been discharged is making sure that proper polarity between the portable battery and the battery to be charged is proper. It is imperative to connect the portable battery and the battery to be charged with proper polarity, i.e. positive to positive terminal connections and negative to negative terminal connections. Failure to do so will rapidly drain the portable battery and further cause serious damage to either or both electrical systems that the two batteries are used in. However, it is often difficult to determine which battery terminal is positive and which is negative because of the accumulation of dirt or lack of lighting.
The polarity problem has been solved by a variety of methods in the battery jumper cable arrangement environment, such as the technique disclosed in U.S. Pat. No. 4,400,658. There is a need for a portable battery charging system that has the polarity problem solved. Such a portable charging system would need to provide a charge or boost to another battery regardless of the charging terminals of the battery to be charged to which the positive or negative terminals of the portable charging system are connected. Such a system would eliminate the problems and dangers associated with incorrect charging battery to discharged battery terminal connections.